Method and device for removing defects on a stationary web of a packaging material

ABSTRACT

The invention relates to a method for removing defects on a stationary web of a packaging material ( 106 ), comprising moving said web of packaging material ( 106 ) through a repair line from a first rotatable roller ( 121 ) to a second rotatable roller ( 122 ) in a first direction, cutting off said web of packaging material ( 106 ) at a first predetermined position, guiding said web of packaging material ( 106 ) of said first roller ( 121 ) into a second direction, wasting said web of packaging material ( 106 ) of said first roller ( 121 ) by movement in said second direction to a waste station, cutting off said web of packaging material ( 106 ) of said first roller ( 121 ) at a second predetermined position, guiding said web of packaging material ( 106 ) of said first roller ( 121 ) back into said first direction, splicing said web of packaging material ( 106 ) of said first roller ( 121 ) back together with said web of packaging material ( 106 ) of said second roller ( 122 ) at said first predetermined position, wherein said method is automated. The invention further relates to a device for removing defects on a stationary web of a packaging material.

BACKGROUND ART

Within packaging engineering, consumer packages of a disposable nature are commonly used for packaging and transporting liquid foods, such as, for example, milk. So-called disposable packages of this type are often made of a laminated packaging material comprising a base layer of paper or cardboard and outer liquid-tight layer of polyethylene. In special cases, such as with particularly oxygen-sensitive foods, for example fruit juice, it is necessary to supplement the packaging material with at least one further layer of a material having oxygen-tight properties, and the most common example of a supplementary material layer of this kind is an aluminium foil between the paper or cardboard layer and one of the two outer liquid-tight layers.

Consumer packages of this sort are nowadays very often produced with the aid of modern rational packaging machines of the sort which, from a web or from prefabricated blanks of the packaging material, both form, fill and also seal finished packages.

Formed, filled and sealed consumer packages are produced from a web, for example, by the web firstly being transformed into a tube by joining together of the two longitudinal edges of the web into a longitudinal liquid-tight sealing joint (normally an overlap sealing joint). The tube is continuously filled with the particular food, for example milk, and is divided into connected pillow-shaped pack units by repeated transversal heat sealings of the tube transversely to the longitudinal axis of the tube below the fill product level of the tube. The filled pillow-shaped pack units are separated from one another by cuts in the transverse seals and may subsequently be given the desired geometric shape by means of at least one further forming and heat sealing operation. Well-known examples of commercial consumer packages of this kind are Tetra Brik and Tetra Classic packages, which are used to transport liquid foods of the type milk, fruit juice, wine and cooking oil.

A laminated packaging material of the sort which is described above is produced on an industrial scale from a roll of a wide web of paper or cardboard. A web which is unwound from the roll is led to a first work station where one side of the web, by suitable printing technology, is provided with a recurring pattern of an aesthetic and/or informative nature. In conjunction with or directly after the printing, the web is also provided with a likewise recurring pattern of weakening lines facilitating folding (so called fold lines). In order to give the subsequently produced disposable packages the desired shape and attractive appearance, it is important that these two recurring patterns are applied to the web in closest possible distance from each other.

The web provided with print and fold lines is led onward to a subsequent work operation, in which the web is coated on both sides with respective outer liquid-tight layers, usually polyethylene. In certain cases, such as when the packaging material is intended for packaging containers for particularly oxygen-sensitive products, the packaging material is also provided with at least one further layer of a material having such barrier properties, for example an aluminium foil, on one side of the packaging material between the paper or cardboard layer and one of the two outer liquid-tight coatings.

Finally, the packaging material web is divided up into individual partial webs, which are wound into finished packaging rolls in order to produce the formed, filled and sealed packaging containers.

In order to ensure that the packaging material in the finished packaging rolls meets set quality requirements and is not beset with serious faults and defects which could jeopardize the chemical and/or mechanical protection of the finished packaging containers, the packaging rolls are subjected to a quality control in which the packaging material is repaired by removing parts with defects, such as possible areas of missed polymer coating, pinholes in material layers, defective aluminium foil, wrinkles, spots, creasing defects or printing defects.

A repair line of the conventional sort has a rotatable horizontal shaft at its one end and a corresponding rotatable horizontal shaft at its other end. Between the rotatable shafts, the repair line has a repair station, in which detected defects are to be removed and treated on a stationary web of the packaging material. Since a packaging material can quite often be beset with a number of production faults and these production faults, in turn, can be found at randomly spread points on one and the same packaging material, this means that a web of the packaging material which is led through the repair station can be subjected to several repair operations, each at a different position along the web of the packaging material roll, where defective packaging material is removed in connection with the quality control. Between the repair operations at stand-still of the web, the web needs to spooled at high speed forward to the next position for a repair operation.

When a roll of packaging material is to be checked and repaired, it is suspended from the horizontal rotatable shaft at one end of the repair line. A web of the packaging material is unwound from the suspended roll and is manually advanced for winding onto the horizontal rotatable shaft at the other end of the repair line. En route to the rotatable shaft at the other end, the web is first led through a device for controlling the axial stress of the web and onward from the device through the work station in which detected production faults are to be treated on the web. Such manual pulling of the web along a U-shaped loop through the known roller arrangement is complicated, labour-intensive and time-consuming whenever a new roll has to be checked and repaired.

The actual repairing of the web is made by manually cutting the web at two places before and after the portion of the in the web of a packaging material having defaults, removing the part between the cuts, and then manually splicing the ends together to form a continuous web of a packaging material again. These operations are time consuming and labour intensive.

An object of the invention is therefore to eliminate the mentioned drawbacks and provide a device of the sort described in the introduction, which device enables a significantly easier and less time-consuming and labour-intensive method for repairing web of a packaging material.

SUMMARY OF THE INVENTION

It is an object of the present invention to improve the current state of the art, to solve the above problems, and to provide an enhanced method for removing defects on a stationary web of a packaging material thereby repairing the web. These and other objects are achieved by a method for removing defects on a stationary web of a packaging material, comprising: moving said web of packaging material through a repair line from a first rotatable roller to a second rotatable roller in a first direction, cutting off said web of packaging material at a first predetermined position, guiding said web of packaging material of said first roller into a second direction, preferably by changing the position of a guiding cylinder, wasting said web of packaging material of said first roller by movement in said second direction to a waste station, cutting off said web of packaging material of said first roller at a second predetermined position, guiding said web of packaging material of said first roller back into said first direction, preferably by changing the position of the guiding roller back to its initial position, and splicing said web of packaging material of said first roller back together with said web of packaging material of said second roller at said first predetermined position, wherein said method is automated.

The automated method reduces labor needs and makes the method faster. Costs are thereby saved in two ways, both by reducing labor costs and by reducing the number of devices needed for removing defects in webs of packaging material. Human errors are also avoided, providing a higher degree of certainty that all errors in a web of packaging material have been removed. Better process control of the splices is also achieved such that the register of packages is kept intact, i.e. the splice may be positioned at a position of the web corresponding to exactly one package such that only one package will end up having a splice.

The method may further comprise the step of stopping said web of packaging material from moving in said first direction before the step of cutting off said web of packaging material at said first predetermined position. The method may further comprise the step of stopping the web of packaging material from moving in said second direction before the step of cutting off said web of packaging material at said second predetermined position. Cutting is easier to perform and the position of the cut will be more precise if the web of packaging material is stopped before it is cut at the first predetermined position.

The method according to the invention may further comprise the step of rewinding said web of packaging material of said second roller from said second roller onto a third rotatable roller. Since the web of packaging material has to be used in the right direction when used in a packaging machine as e.g. a filling machine for the print of the web of packaging material to be in the correct orientation on the package, the web of packaging material rolled onto the second roll has to be re-winded onto the third roll before it can be distributed further and finally used to make packages.

The method according to the invention may further comprise, as a first step, the step of receiving information regarding said defects of said web of packaging material from a control unit. An inline quality control device may e.g. be used at an earlier stage in a factory for web of packaging material for scanning the web of packaging material for errors. The lengthwise location of the errors may thus be logged and stored together with the identification of the reel with web of packaging material. If errors are detected, the reel will be moved to a device for removing defects and the method described herein will be applied to the web of packaging material.

The method according to the invention may further comprise the step of controlling the tension of said web of packaging material in a longitudinal direction of said web of packaging material by means of a tension control device. Tension control is important so that the web of a packaging material is not damaged during the repairing operation.

The invention further relates to a device for removing defects on a stationary web of a packaging material, comprising a first rotatable roller and a second rotatable roller, said web of packaging material being wound from said first roller to said second roller in a first direction, a guiding unit adapted to guide said web of packaging material of said first roller between said first direction and a second direction, preferably by means of a moveable guiding cylinder forming part of the guiding unit, a cutting device adapted to cut off said web of packaging material at a first predetermined position and at a second predetermined position, a wasting station arranged along second direction and adapted to collect said web of packaging material being cut off between said first predetermined position and said second predetermined position, and a splicing unit adapted to splice said web of packaging material of said first roller back together with said web of packaging material of said second roller, wherein said device is automated.

The device according to the invention may further comprise at least one tension control device, or dancer roller as they are called, adapted to provide a pressure onto said web of packaging material in a normal direction to the web of packaging material surfaces in order to provide a tension of the web of packaging material between said first rotatable roller and said second rotatable roller.

The device may further comprise a third roller, said web of packaging material being wound from said second roller to said third roller so as to rewind said web of packaging material, and a control unit arranged to control the device.

The splicing unit of the device may comprise an induction sealing device for sealing the open ends together in the splicing unit.

A person skilled in the art understands that the same advantages as discussed in relation to the features of the inventive method are also true for the corresponding features of the inventive device.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to “a/an/the [element, device, component, means, step, etc.]” are to be interpreted openly as referring to at least one instance of said element, device, component, means, step, etc., unless explicitly stated otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects, as well as additional objects, features and advantages of the present invention, will be more fully appreciated by reference to the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic view of a device for removing defects on a stationary web of a packaging material.

FIG. 2 is a schematic view of a device for removing defects on a stationary web of a packaging material where the web of a packaging material is cut and fed to waste station.

FIG. 3 is a schematic view of a tension control device adapted to be placed in the device of FIG. 1 and FIG. 2 in some embodiments.

FIG. 4 is a block diagram showing a method for removing defects on a stationary web of a packaging material.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows a device for removing defects on a stationary web of a packaging material. A reel 102 of stationary web of a packaging material 106 is placed on a first rotatable roller 121. At start-up, the leading edge of the stationary web 106 is pulled by a robotic arm (not shown) to the second rotatable roller 122. The reel 102 of stationary web of a packaging material 106 is spooled from the first rotatable roller 121 into a second reel 104 on the second rotatable roller 122.

The stationary web 106 is bent around a present pull- and break arrangement 110, which comprises a first guiding cylinder 112 and a second guiding cylinder 114, both being arranged to rotate around a first rotational axis 116 and a second rotational axis 118 respectively. As will be explained below, at least one of the guiding cylinders 112, 114 are moveble such that the web path can be changed depending on the position of the at least one guiding roller 112, 114.

During a doctoring process the operative position of the pull- and break arrangement 110 is such that the web is guided along an S-shaped path through the arrangement 110. In the present setup the first guiding cylinder 112 is arranged above the second guiding cylinder 114. The web is guided below and around about half the second cylinder on the far side thereof, as seen from the first reel 102 before following the second cylinder around about half its circumference before continuing towards a doctoring station 108 and the second reel 122. The first guiding cylinder 112 is illustrated in full lines while various positions for the second guiding cylinder 114 are shown in dotted lines. As seen in FIG. 2, there is a position P1 corresponding to the position as shown in FIG. 1; i.e. an “operative position” for guiding the web 106 towards the second reel 122. There is a position P2 which corresponds to an “engagement position” which is more of an intermediate position passed when moving between the other positions. There is a “waste position” P3 in which the arrangement 110 will guide a passing web 106 downwards. There is also a “thread position” P4 in which the second guiding cylinder 114 is fully disengaged with the first guiding cylinder 112 such that a web 106 may be conveniently arranged (or threaded) through the arrangement 110 merely by following a rectilinear path from the first reel 121 to the second reel 122. The first guiding cylinder 112 is arranged to rotate around a first axis 116. The second guiding cylinder 114 is arranged to rotate around a second axis 118. The first and the second guiding cylinders are arranged in parallel, i.e. having parallel rotational axes. In one or more embodiments both guiding cylinders 112, 114 are suspended from one side axial thereof only, basically corresponding to the rotational axis of each cylinder having one end attached to a constructional arrangement while the second end is free.

In the view of FIG. 2 the second guiding cylinder 114 has been arranged in the waste position P3. In this position the second guiding cylinder 114 is in contact with the first guiding cylinder 112, with the intermediate of the web 106, and the tangent of the contact, i.e. nip, is directed downwards, enabling guiding of the web 106 in an alternative direction. In the present embodiment the web 106 is directed towards a waste assembly schematically indicated by the recycling bin. Wasting of packaging material may be the first operation after threading of a web. This means that the second guiding cylinder 114 is moved from the position P4, to position P2, and then to the waste position P3. One other example could be that the second guiding cylinder 114 is moved from the first position P1 directly to the waste position P3. No matter the scenario the present arrangement nevertheless enables the second guiding cylinder 114 to assume the position P3.

When the automatic repairing process is finished, the packaging material 106 spooled onto the reel 122 is spooled onto the reel 123, see FIG. 2, so that the packaging material is wound in the same order as when entering the device for removing defects. The device of the invention further comprises a control unit 125, controlling the automated process of the entire device for removing defects on a stationary web of a packaging material.

FIG. 3 illustrates a tension control device 201. A stoppage of the web can generally be performed without major problems, but, on the other hand, problems and disruptions quite often arise in connection with the restart of the web after each stoppage and standstill. Problems and disruptions of this sort are at least partially associated with the fact that a moving web 106 of a packaging material cannot be stopped instantaneously, but rather that a slowdown and stoppage of the web, due to inherent inertia and other dynamic effects, takes place after a continuous retardation process, during which a growing accumulation or loop of the slowing web is formed in conjunction with or immediately before the repair station 108. When the web 106, after its standstill, is then started and reaccelerated, this accumulation or loop of the web will gradually shrink and finally disappear altogether. At the same moment, the web will thus be subjected to an axial pull, which at the same time subjects the web to an instantaneous strong axial force in the motional direction of the web.

In order to prevent this instantaneous axial force from becoming so large that it even exceeds the ultimate tensile strength of the particular web, the repair line of FIG. 1 and FIG. 2 may be equipped with a tension control device 201 according to the invention for controlling axial forces upon a web and keeping these at a level below this ultimate tensile strength. The tension control device 201 may e.g. be placed before the pull-and-brake device 110 shown in FIG. 1 and FIG. 2, i.e. at a position between the first reel 121 and the pull- and break assembly 110.

The tension control device 201 has a first cylinder 204, which is rotatable about a first horizontal shaft, a second cylinder 205, which is rotatable about a second horizontal shaft, and a third rotatable cylinder 203, which is rotatable about a third horizontal shaft. The third rotatable cylinder 203 is movable, in response to axial forces acting upon the web at any moment, between a lower position and an upper position along an arc-shaped motional path (shown in dashed representation) in the vertical plane between the two first and second rotatable cylinders 204 and 205, the arc being defined by the end of the arm 202 that the third cylinder 203 is attached to.

In order to counter strong axial forces upon the web in connection with pulls when the speed of the web is accelerated, the third rotatable cylinder 203 is biased with a freely adjustable force which acts in the direction of the motion of the third cylinder from the lower position. Such a counterforce can be produced in a known manner with both pneumatic and hydraulic and mechanical means which act directly upon the fourth rotatable shaft. In order to avoid rupture of the web due to excessively strong pulls and axial forces upon the web, as is described above, this counterforce must be set at a value below the particular ultimate tensile strength of the web. If the web, for example, has an ultimate tensile strength in the order of magnitude of 20,000 N, then the counterforce can be set at a value amounting to just one tenth ( 1/10) of this, such as 1800-2000 N, in order thus to enable the third cylinder to be displaced, if the web is acted upon by axial forces, already far below the ultimate tensile strength of the web.

FIG. 4 illustrates the automated method for removing defects on a stationary web of a packaging material performed by the device of FIGS. 1-3. The device receives information regarding defects of the web of packaging material from a control unit indicating to the device where defects are present on the packaging material. The packaging material is moved from a first rotatable roller to a second rotatable roller and stopped from moving in first direction at a position corresponding to the information received regarding locations of defects. The web of packaging material is then cut off at that first predetermined position, as indicated by the position of the cutting knife 124 in FIG. 1 or 2. The cutting knife 124 is preferably a sharp tool being moveable across the width of the web 106 for separating the web into a leading end, and a trailing end. The web of packaging material is thereafter guided into a second direction to a waste by changing the position of the second guiding roller 114. The web of packaging material of said first roller containing defect is thereby moved in the second direction into a waste station. When the defect section has been wasted, the web of packaging material is stopped from moving into the waste station in the second direction. The web of packaging material is cut off at that second predetermined position where defects are no longer present. This may e.g. be performed by moving the cutting knife 124 towards the right in FIG. 2, such that it engages at a position upstream the pull- and break assembly 110, and activating the cutting knife 124 thus providing a lateral cut across the width of the web 106. The web of packaging material of said first roller is again guided into the first direction by returning the second guiding roller 114 to its position P1 and pulling of the packaging material by the robotic arm, and is spliced back together, preferably by means of induction heating or other heat-generating device, with the web of packaging material of the second roller 122 at the first predetermined position by means of repair station 108. The defective parts have thus been automatically cut off and been removed and the web packaging material has been reattached.

The skilled person realizes that a number of modifications of the embodiments described herein are possible without departing from the scope of the invention, which is defined in the appended claims. 

1. A method for removing defects on a stationary web of a packaging material, comprising; moving said web of packaging material through a repair line from a first rotatable roller to a second rotatable roller in a first direction, cutting off said web of packaging material at a first predetermined position, guiding said web of packaging material of said first roller into a second direction, wasting said web of packaging material of said first roller by movement in said second direction to a waste station, cutting off said web of packaging material of said first roller at a second predetermined position, guiding said web of packaging material of said first roller back into said first direction, splicing said web of packaging material of said first roller back together with said web of packaging material of said second roller at said first predetermined position, wherein said method is performed under control of a controller.
 2. The method of claim 1, wherein guiding the web of packaging material into a second position is performed by changing the position of a guiding cylinder, and wherein guiding the web of packaging material back into the first direction is performed by returning the guiding cylinder to its initial position.
 3. The method of claim 1, further comprising the step of stopping said web of packaging material from moving in said first direction before the step of cutting off said web of packaging material at said first predetermined position.
 4. The method of claim 1, further comprising the step of stopping said web of packaging material from moving in said second direction before the step of cutting off said web of packaging material at said second predetermined position.
 5. The method according to claim 1, further comprising the step of rewinding said web of packaging material of said second roller from said second roller onto a third rotatable roller.
 6. The method according to claim 1, further comprising, as a first step, the step of receiving information regarding said defects of said web of packaging material from a control unit.
 7. The method according to claim 1, further comprising the step of controlling the tension of said web of packaging material in a longitudinal direction of said web of packaging material by means of a tension control device.
 8. A device for removing defects on a stationary web of a packaging material, comprising: a first rotatable roller and a second rotatable roller configured to wind said web of packaging material being wound from said first roller to said second roller in a first direction, a guide adapted to guide said web of packaging material of said first roller between said first direction and a second direction, a cutter adapted to cut off said web of packaging material at a first predetermined position and at a second predetermined position, a wasting station arranged along said second direction and adapted to collect said web of packaging material being cut off between said first predetermined position and said second predetermined position, and a splicer adapted to splice said web of packaging material of said first roller back together with said web of packaging material of said second roller.
 9. The device of claim 8, wherein said guide comprises at least one guiding cylinder being configured to be moveable between at least two positions, whereby guiding the web of packaging material into a second position is performed by changing the position of the at least one guiding cylinder, and whereby guiding the web of packaging material back into the first direction is performed by returning the at least one guiding cylinder to its initial position.
 10. The device according to claim 8, further comprising at least one tension control device adapted to provide a pressure onto said web of packaging material in a normal direction to the web of packaging material surfaces so as to provide a tension of the web of packaging material between said first rotatable roller and said second rotatable roller.
 11. The device according to claim 8, further comprising a third roller, said web of packaging material being wound from said second roller to said third roller so as to rewind said web of packaging material.
 12. The device according to claim 8, wherein said splicer comprises an induction sealing device.
 13. The device according to claim 8, further comprising a controller arranged to control operation of the device. 